1. Field of the Invention
The present invention relates to an apparatus for capturing a cell for injecting a substance such as a gene or drug into the cell. More specifically, the invention relates to an apparatus that allows observation of the cell while the substance is being injected in the cell.
2. Description of the Related Art
The injection (introduction) of genes or drugs into cells using a needle to alter their properties has recently been carried out in the life science fields, and particularly in the fields of regenerative medicine and genome drug development. When injecting a gene or drug into a cell, it is necessary to immobilize the cell to prevent it from moving. A cell immobilizing plate (hereinafter, “cell capturing plate”) has been conventionally used to immobilize a cell. The cell capturing plate has a plurality of microscopic capturing holes. The diameter of these holes is smaller than that of the cells. The diameter of the cells can vary from 10 micrometers to 100 micrometers depending on the type of the cells. Cells are caught, and thereby immobilized, in these holes when the cells, or a liquid containing the cells, is aspirated from the other side of the cell immobilizing plate with an aspiration pump.
A microinjection method has been developed as a method for injecting a gene or drug directly into a cell through a needle. In the microinjection method, an ultrafine needle having a diameter of 1 micrometer or less (tip outer diameter: 1 micrometer, inner diameter: about 0.5 micrometers) and filled with a drug is inserted into a cell and the drug is injected into the immobilized cell. This process is performed while observing the cell and the needle under a microscope.
Petri dishes used in the conventional cell capturing apparatus require a capturing plate that captures cells, a well for holding a cell turbid solution, and on the bottom, a connection for an aspiration tube from an aspiration pump used to aspirate cells into microscopic capturing holes in the capturing plate. Consequently, a structure is mainly employed for conventional Petri dishes for cells in which microscopic holes are formed at predetermined positions in a Petri dish, a cell capturing plate is adhered to form a well, and the Petri dish is placed on a unit that was machined to serve as an aspiration connector from an aspiration pump.
FIG. 17 is a schematic block diagram of a Petri dish used in a conventional cell capturing apparatus. A cell turbid solution is contained inside a Petri dish 100a, a through hole 112 is formed approximately in the center of the Petri dish 100a, and a capturing plate 30 is fixed on the through hole 112 by adhesion and the like.
A plurality of micropores 330 are formed in the capturing plate 30. Cells are captured in these micropores 330 by aspirating the cell turbid solution from below with an aspiration pump 200 through the through hole 112. The captured cells can be observed with a microscope (not shown) from above the Petri dish 100a. 
Conventional techniques relating to capturing of cells have been disclosed, for example, in Japanese Patent Application Laid-open No. 2004-180555 and Japanese Patent Application Laid-open No. 2004-163.
In the conventional Petri dish 100a, there has been a problem of the occurrence of leakage from a gap between the Petri dish 100a and the capturing plate 30, thereby preventing the necessary cells from being aspirated (captured) reliably.
It is a common practice to observe the cells with a transmitted light. Since the well and aspiration connection are molded into a single unit as a result of machining in a conventional Petri dish as previously described, however, the machined surface on the bottom of the capturing plate cannot be optically polished, thereby resulting in the problem of being unable to observe the cells from below the capturing plate with transmitted light.
Furthermore, there are no particular considerations given to the handling of injected cells, which are cells in which a substance has been injected, and empty cells, which are cells in which the substance has not been injected because they are not suitable for injection of the substance. Since a technique capable of distinguishing between these injected cells and empty cells has not been examined, a method of distinguishing these injected cells and empty cells is desired.